1. Field of the Invention
The present invention relates to a wireless communicating method, a wireless communicating system, a communicating station, and a controlling station suitable for wirelessly transmitting chronologically continuous data streams (such as digital audio data and digital video data) and asynchronous data (such as commands) between for example digital audio units or between digital video units.
2. Description of the Related Art
Audio units and video units have been digitized as with for example CD (Compact Disc) players, MD (Mini Disc) recorders/players, digital VCRs, digital cameras, and DVD (Digital Versatile Disc) players. As personal computers have become common, systems that connect such digital audio units or digital video units to personal computers have been proposed. As an interface that accomplishes a system that connects such digital audio units or such digital video units to a personal computer, IEEE (Institute of Electronics Engineers) 1394 is becoming attractive.
The IEEE 1394 interface supports both an isochronous transmission mode and an asynchronous transmission mode. The isochronous transmission mode is suitable for transmitting chronologically continuous data streams such as video data and audio data at high speed. The asynchronous transmission mode is suitable for transmitting various commands and files. Since the IEEE 1394 interface supports both the isochronous transmission mode and the asynchronous transmission mode, when the IEEE 1394 interface is used, video data and audio data can be transmitted between digital audio units and between digital video units, respectively. With a personal computer connected to such digital units through the IEEE 1394 interface, the user can easily control and edit video data and audio data.
The IEEE 1394 interface is a wired interface. To structure such a system with a wired interface, cable connections are required. In addition, such cable connections tend to become complicated. Moreover, with a wired interface, it is difficult to connect units that are disposed in different rooms.
Thus, a digital audio unit or a digital video unit and a personal computer are connected with a wireless LAN (Local Area Network) so as to wirelessly communicate therebetween. As examples of the wireless LAN, CSMA (Carrier Sense Multiple Access) method and polling method are known.
However, in the conventional CSMA method and polling method, data streams such as video data and audio data cannot be transmitted at high speed. To solve such a problem, as with IEEE 1394, a wireless LAN that supports both an isochronous transmission mode that allows data streams such as video data and audio data to be transmitted at high speed and an asynchronous transmission mode that allows asynchronous data such as commands and files to be transmitted has been developed.
When data is wirelessly transmitted between units through the wireless LAN, it is preferable to assign a priority level to transmission data so as to allow data to be transmitted with priority corresponding to the assigned priority level. For example, when parameters are exchanged in the initial setting state, it is desired that a response to a parameter should be promptly sent back. In this case, the priority level is raised so as to perform a communication with priority.
In the polling method, by varying the frequency of acquisition of communication right, a priority level can be assigned. Particularly, in a polling communication, since a controlling station manages access right, a priority level can be easily and securely assigned.
However, when a communicating station need to transmit data in emergency, even if it changes the priority level, it cannot transmit a priority level change request to the controlling station in the case that the communication system gets congested.
Therefore, an object of the present invention is to provide a wireless communicating method, a wireless communicating system, a communicating station, and a controlling station that allow access right of each communicating station to be easily changed and controlled corresponding to a priority level assigned thereto.
A first aspect of the present invention is a wireless communicating method of a system having a plurality of communicating stations and a controlling station for causing the communicating stations to be accessed, comprising the steps of transmitting a communication signal between each of the communicating stations and the controlling station, the communication signal being structured as a frame divided as time periods of a control area and a data area, causing the controlling station to transmit a communicating station state signal to each of the communicating stations, causing each of the communicating stations to transmit a communicating station state change request signal to the controlling station so as to cause the controlling station to control access right of the communicating station corresponding to a priority level assigned to the communicating station.
A second aspect of the present invention is a wireless communicating system, comprising a plurality of communicating stations, and a controlling station for causing the communicating stations to be accessed, wherein a communication signal is transmitted between each of the communicating stations and the controlling station, the communication signal being structured as a frame divided as time periods of a control area and a data area, wherein the controlling station transmits a communicating station state signal to each of the communicating stations, and wherein each of the communicating stations transmits a communicating station state change request signal to the controlling station so as to cause the controlling station to control access right of each of the communicating stations corresponding to a priority level assigned to each of the communicating stations.
A third aspect of the present invention is a communicating station of a wireless communicating system having a plurality of communicating stations and a controlling station for causing the communicating stations to be accessed, a communication signal being transmitted between each of the transmitting stations and the controlling station and structured as a frame divided as time periods of a control area and a data area, comprising a communicating station state change request signal transmitting means for transmitting a communicating station state change request signal that causes a priority level of each of the communicating stations to be changed, and a communicating station state signal receiving means for receiving the communicating station state signal from the controlling station, wherein the priority level of each of the communicating stations is updated, the communicating station transmits the communicating station state change request signal to the controlling station, receives the communicating station state signal from the controlling station, and acknowledges that the priority level has been updated.
A fourth aspect of the present invention is a control station of a wireless communicating system having a plurality of communicating stations and a controlling station for causing the communicating stations to be accessed, a communication signal being transmitted between each of the transmitting stations and the controlling station and structured as a frame divided as time periods of a control area and a data area, comprising a communicating station state change request signal receiving means for receiving a communicating station state change request signal from each of the communicating stations, the communicating station state change request signal causing a priority level of each of the communicating stations to be changed, a communicating station state signal transmitting means for transmitting a communicating station state signal that causes the state of each of the communicating stations to be set corresponding to the communicating station state change request signal, and a controlling means for controlling access right corresponding to the priority level of each of the communicating stations, wherein after the controlling station receives the communicating station state change request signal from each of the communicating stations, the controlling station transmits the communicating station state signal corresponding to a requested priority level and changes the access right of each of the communicating stations corresponding to a priority level assigned thereto.
A communication signal transmitted and received between each communicating station and a controlling station is structured as frames each of which is divided into a time period of a control area and a time period of a data area. In the control area, a communicating station state signal and a communicating station state change request signal are placed. The communicating station state signal represents the priority level of the local communicating station. The communicating station state change request signal causes the priority level of the local communicating station to be changed. In such a manner, the control area and the data area are chronologically divided. In addition, the controlling station transmits the communicating station state signal to the communicating station and the communicating station transmits the communicating station state change request signal to the controlling station so that the controlling station controls the access right of the communicating station corresponding to the priority level assigned thereto. Thus, in any case, the priority level of each communicating station can be securely assigned.
These and other objects, features and advantages of the present invention will become more apparent in light of the following detailed description of a best mode embodiment thereof, as illustrated in the accompanying drawings.